Conventionally proposed as physicochemical reactive decomposition methods for biomass and other such organic substances and the like, there are—in addition to known chemical oxidation methods, photooxidation methods, combustion methods, and hydrothermal methods—decomposition-type treatment methods employing supercritical fluids such as are disclosed at Japanese Patent Application Publication Kokoku No. H1-38532 (1989) and so forth.
Unlike reactive hydrothermal methods employing low-temperature conditions of 200° to 300° C. as reaction conditions, such decomposition-type treatment methods for organic substances and the like employing supercritical fluids use supercritical water at conditions exceeding the critical pressure of 218 atmospheres and the critical temperature of 374° C. of water to decompose organic substances and other such reactant substances. This supercritical water possesses excellent advantages such as the fact that the polar nature thereof can be controlled based on temperature and pressure, permitting solubilization of paraffinic hydrocarbons, benzene, and other such nonpolar substances; the fact that it displays extremely excellent properties as reaction solvent for oxidative decomposition of organic matter in that it mixes in arbitrary ratios even with oxygen and other such gases, and also the fact that because it is possible to raise temperature to the critical temperature or higher using only heat of oxidation where the fractional carbon content of the material being decomposed is several percent, it is extremely excellent from a thermal energy standpoint as well; and the fact that by using supercritical water it is possible through hydrolytic reaction and/or thermolytic reaction to more or less completely decompose almost any kind of decomposition-resistant organic matter, poisonous organic matter, or the like.
Conventional reactive decomposition methods employing supercritical fluids are carried out according to the following sequence. To wit, three fluids or sets of fluids—these being water including organic substance(s) and/or other such reactant substance(s); oxygen and/or other such oxidant fluid(s); and supercritical fluid(s)—are supplied in previously mixed state(s) or partially mixed state(s) to reaction vessel(s) carrying out supercritical hydration reaction(s), and the material in question is decomposed through oxidative process(es) under conditions which are supercritical with respect to water. By further causing oxidation reaction(s) to proceed, it is also possible for the material in question to be processed as far as carbon monoxide, hydrogen, and/or the like.
Conventional reaction apparatuses employing supercritical fluids have in common the fact that fluid(s) are pressurized and are thereafter heated, causing fluid(s) to assume supercritical state(s) or subcritical state(s)—such state(s) being high-temperature, high-pressure state(s)—as a result of which reaction is made to occur. This being the case, a great deal of energy is required when fluid(s) are made to assume high-temperature, high-pressure state(s).
Methods for reducing energy during pressurization in the case of supercritical-fluid and/or subcritical-fluid high-temperature, high-pressure fluid(s) include the development of the continuous autoclave utilizing the pipeline system (Nakamichi Yamasaki, Suinetsu Kagaku Jikkensho Houkoku, Vol. 3 1-4 (1979). In this method, piston(s) and cylinder(s) are used to recover pressure from post-treatment high-temperature, high-pressure fluid(s); and reduction in energy during pressurization of unpressurized fluid(s) is achieved through use of other piston(s) and cylinder(s) linked to piston(s) used for recovery.
For reducing energy during pressurization in the case of supercritical-fluid and/or subcritical-fluid high-temperature, high-pressure fluid(s), there is also the method using the apparatus disclosed at Japanese Patent Application Publication Kokai No. H12-233127 (2000). This apparatus is provided with second drive means accepting the load of the driving force from first drive means employing piston(s) within cylinder(s) to receive pressure from post-treatment high-temperature, high-pressure fluid(s) and transmitting same as force to pressurize pre-treatment fluid(s). That is, the apparatus is such that, after being reduced using back pressure valve(s), energy of post-treatment high-pressure fluid(s) is introduced into cylinder(s) at the aforesaid first drive means. The apparatus is such that this permits fluid(s) including reactant substance(s) to be made to assume high temperature(s) and high pressure(s) and to be supplied in stable fashion to reaction system(s).
Furthermore, because supercritical fluid(s) and/or subcritical fluid(s) are at high temperature and high pressure, decomposition reaction(s) and so forth occurring within fluid(s) proceed extremely rapidly. For this reason, it is necessary to employ short time(s) for treating reactant substance(s) with supercritical fluid(s) and/or subcritical fluid(s) and to quickly stop the rapid reactions which occur within supercritical fluid(s) and/or within subcritical fluid(s).
Methods for shortening time for rapid treatment of reactant substance(s) with supercritical-fluid and/or subcritical-fluid high-temperature, high-pressure fluid(s) include methods employing continuous reaction apparatuses for cellulose hydrolysis (M. Sasaki, B. Kabyemela, R. Malaluan S. Hirose, N. Takeda, T. Adschiri, K. Arai; Cellulose hydrolysis in subcritical and supercritical water, J. Supercrit. Fluids 1998. 13. 261-268.). This method is carried out using a flow-type reaction apparatus, treatment of reactant substance(s) being carried out according to the following sequence. To wit, reactant substance(s) are directly mixed in the vicinity of reaction vessel inlet(s) with supercritical water which has been heated and pressurized under prescribed conditions, rapidly raising the temperature thereof until target optimum reaction temperature(s) are reached. Furthermore, at reaction vessel outlet(s), rapid cooling is carried out through external cooling by direct delivery of cold water to reaction liquid(s). In such case, shortening of the time for treating reactant substance(s) with supercritical water is made possible by reducing reaction vessel volume and/or increasing flow rate.
However, the reality at present is that there is not yet an industrial reaction apparatus for handling supercritical state(s) of high-temperature, high-pressure fluid(s), such as would permit recovery of energy as well as treatment of reactant substance(s) with supercritical fluid(s) in extremely short period(s) of time, and such as would also permit the aforementioned conventional reaction(s) of organic substance(s) and/or the like with supercritical fluid(s) to be implemented efficiently.
With conventional reaction apparatuses for organic substance(s) and/or the like employing supercritical fluid(s), e.g., where reactant substance(s) are wood meal and/or other such organic substance(s), water under high pressure and wherein organic substance(s) have been dispersed is rapidly heated and is maintained in supercritical and/or subcritical state(s) for fixed period(s) of time, hydrolytic reaction(s) occurring while in such supercritical and/or subcritical state(s) permitting saccharification reaction(s) to be carried out wherein wood meal and/or other such organic substance(s) are made into glucose and/or other such low-molecular-weight sugar(s). In order to prevent the low-molecular-weight saccharide(s) produced after the conclusion of such saccharification reaction(s) from being decomposed further, it is necessary to rapidly cool the high-temperature supercritical water and/or subcritical water and stop the reaction(s). Such saccharification reaction(s) may be carried out using either a batch-type apparatus or a flow-type apparatus. Conventionally proposed reaction apparatuses, where implemented in the context of flow-type apparatuses, make use of apparatus constitutions employing processes wherein realization of high-temperature supercritical water state(s) occurs as a result of mixing of low-temperature, supercritical-pressure water wherein wood meal is dispersed with high-temperature supercritical water and causing reaction(s) to proceed, and wherein stopping of such reaction(s) is carried out through injection of cold water therein.
However, when carrying out the aforesaid processes with such conventional reaction apparatuses, problems such as the following remain.    (1) Apparatus constitution requires pressurizing, heating, reacting, cooling, and decompressing vessels into which water is sequentially introduced, making apparatus constitution complicated overall.    (2) Because time for saccharification reaction of ligneous and/or other such organic substance(s) is short, cold water must be mixed therewith to stop reaction. If reaction time is increased, reactant substance(s) are overdecomposed, preventing sugars from being obtained.    (3) Because reaction is stopped by rapid cooling with cold water, much water is used. For this reason, the process of concentrating sugar(s) following reaction is made complicated.    (4) The fact that the cooling process is carried out using cold water means that energy consumption is high.    (5) It is difficult to achieve distribution in such state that ligneous and/or other such organic substance(s) are uniformly dispersed in water at high pressure.
It is therefore an object of the present invention to provide a reaction apparatus for organic and/or other substance(s) employing supercritical fluid(s) and/or subcritical fluid(s) permitting injection of organic substance(s) and/or other reactant substance(s) in homogeneous state(s) to reactor(s) and permitting treatment of reactant substance(s) with supercritical fluid(s) to occur in extremely brief period(s) of time, and also permitting actuation to occur in industrial fashion and at high energy efficiency.